IgG4-related disease is a recently recognized multi-organ disorder characterized by high levels of serum IgG4 and dense infiltration of IgG4-positive cells into several organs. Although the pancreas was the first organ recognized to be affected by IgG4-related disorder in the syndrome of autoimmune pancreatitis, we present here clinico-pathological features of 23 patients diagnosed as having renal parenchymal lesions. These injuries were associated with a high level of serum IgG4 and abundant IgG4-positive plasma cell infiltration into the renal interstitium with fibrosis. In all patients, tubulointerstitial nephritis was the major finding. Although 14 of the 23 patients did not have any pancreatic lesions, their clinicopathological features were quite uniform and similar to those shown in autoimmune pancreatitis. These included predominance in middle-aged to elderly men, frequent association with IgG4-related conditions in other organs, high levels of serum IgG and IgG4, a high frequency of hypocomplementemia, a high serum IgE level, a patchy and diffuse lesion distribution, a swirling fibrosis in the renal pathology, and a good response to corticosteroids. Thus, we suggest that renal parenchymal lesions actually develop in association with IgG4-related disease, for which we propose the term 'IgG4-related tubulointerstitial nephritis.'
Long-term follow-up for IgG4-related kidney disease, including relapse information, is sparse. To gather data on this we retrospectively examined the clinical course of 43 patients with IgG4-related kidney disease, in which most patients were treated with, and maintained on, corticosteroids. One month after the start of treatment, most of the abnormal serology and radiology parameters had improved. In 34 of the steroid-treated patients whose follow-up period was more than 12 months (median 34 months), excluding one hemodialysis patient, the estimated glomerular filtration rate (eGFR) before treatment was over 60 ml/min in 14 patients (group A) and under 60 ml/min in 20 patients (group B). In group A, there was no difference between the eGFR before therapy and at the last review. In group B, the mean eGFR before treatment (34.1 ml/min) was significantly improved after 1 month (45.0 ml/min), and renal function was maintained at a similar level through last follow-up. Among 24 evaluated patients at the last review, however, renal atrophy had developed in 2 of 9 in group A and in 9 of 15 in group B. Relapse of IgG4-related lesions occurred in 8 of 40 treated patients. Thus, the response of IgG4-related kidney disease to corticosteroids is rapid, not total, and the recovery of renal function persists for a relatively long time under low-dose maintenance. A large-scale prospective study to formulate more useful treatment strategies is necessary.
Background/Aims: Our previous comprehensive analysis of the genes expressed in kidneys with anti-glomerular basement membrane (GBM) nephritis using DNA microarrays showed that SM22α was one of the highly expressed genes. SM22α is a 22-kDa cytoskeletal protein that is exclusively expressed in smooth muscle cells. We investigated the localization of SM22α at mRNA and protein levels, and its pathological significance in anti-GBM nephritis kidneys. Methods: Northern blot analysis, in situ hybridization, immunohistochemistry and double immunofluorescence studies were performed. The specific antibody (Ab) against SM22α was obtained by immunization of rabbits with recombinant rat SM22α protein. Results: SM22α mRNA expression was upregulated in kidneys and inducibly expressed in the parietal and visceral glomerular epithelial cells in anti-GBM nephritis kidneys. Immunohistochemistry with anti-SM22α Ab showed that SM22α protein was localized in the same series of cells. Double immunofluorescence with anti-SM22α and anti-glomerular cell markers demonstrated that SM22α might be expressed in epithelial cells of injured glomeruli. In visceral epithelial cells, SM22α might be expressed in cells in which podocyte specific markers, podocalyxin and nephrin were lost. Conclusion: The injured glomerular epithelial cells in anti-GBM nephritis might undergo structural and functional alterations, including the expression of a smooth muscle marker, SM22α.
Summary Background and objectives Previous reports of Fabry disease screening in dialysis patients indicate that α-galactosidase A activity alone cannot specifically and reliably identify appropriate candidates for genetic testing; a marker for secondary screening is required. Elevated plasma globotriaosylsphingosine is reported to be a hallmark of classic Fabry disease. The purpose of this study was to examine the usefulness of globotriaosylsphingosine as a secondary screening target for Fabry disease. Design, setting, participants, & measurements This study screened 1453 patients, comprising 50% of the male dialysis patients in Niigata Prefecture between July 1, 2010 and July 31, 2011. Screening for Fabry disease was performed by measuring the plasma α-galactosidase A enzyme activity and the globotriaosylsphingosine concentration, by high-performance liquid chromatography. Genetic testing and genetic counseling were provided. Results A low level of plasma α-galactosidase A activity (≤4.0 nmol/h per milliliter) was observed in 47 patients (3.2%). Of these, 3 (0.2%) had detectable globotriaosylsphingosine levels. These patients all had α-galactosidase A gene mutations: one was p.Y173X and two were the nonpathogenic p.E66Q. The patient with p.Y173X started enzyme replacement therapy. Subsequent screening of his family identified the same mutation in his elder sister and her children. Genetic testing for 33 of the other 44 patients detected 7 patients with p.E66Q. Thus, the plasma lyso-Gb3 screen identified Fabry disease with high sensitivity (100%) and specificity (94.3%). Conclusions Plasma globotriaosylsphingosine is a promising secondary screening target that was effective for selecting candidates for genetic counseling and testing and for uncovering unrecognized Fabry disease cases.
We report an elderly man with chronic tubulointerstitial nephritis (TIN) showing a high serum immunoglobulin G4 (IgG4) concentration. His serum creatinine (Scr) level had gradually increased from 0.9 mg/dL to 5.6 mg/dL over 18 months. Renal biopsy showed marked IgG4-positive plasma cell infiltration in the interstitium without glomerular abnormalities and IgG4-related TIN was diagnosed. Oral prednisolone reduced his Scr and IgG4 levels immediately. The present case indicates that IgG4-related TIN can not only progress rapidly but also chronically over a long period without significant urinary abnormalities, and we should consider hidden IgG4-related TIN in cases of chronic renal insufficiency.
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